USO — the United States Oil Fund — is caught in an intensifying standoff: the fund has rallied 32% over the past month, yet bearish positioning has never been heavier, and the cost of maintaining that bet just hit its highest level in recent history.
The borrow market is at maximum stress. Availability dropped to exactly zero on May 19 — every single share in the lending pool is lent out, with no capacity remaining for new borrows. That zero-availability reading has been essentially continuous since early May, interrupted only by brief, small windows of supply. What has changed this week is the price of holding the position: cost to borrow jumped to 18.6% APR on May 19, up 70% in a week and a fresh peak for the period tracked. The message from the lending market is unambiguous — shorts are paying more than ever for a position with no room left to grow through direct borrowing.
Short interest itself keeps climbing regardless. It rose nearly 4% week-on-week to reach 108.5% of free float — a level that, as noted in prior coverage, can only be sustained by synthetic exposure through options or swaps rather than outright share borrowing. The month-on-month increase is 28%. Shorts have been adding through the entire rally, absorbing a 32% price gain over 30 days without reducing their exposure. That persistence at increasing cost is the defining feature of this setup.
The options market tells a similar story, though without the recent escalation. The put/call ratio at 1.60 is almost exactly in line with its 20-day average of 1.59 — a z-score near zero. Puts still heavily outnumber calls, consistent with the prevailing bearish lean, but there is no fresh escalation in options-market hedging this week. The PCR has actually drifted slightly lower since mid-May, when it was running closer to 1.72. The borrow market is tightening hard; options positioning is holding steady rather than accelerating alongside it.
Morgan Stanley stands out among institutional holders, reported as the largest disclosed holder at roughly 14% of shares outstanding as of March 31, having added nearly 1.95 million shares in the most recent quarter. That is a significant build in an ETF with a free float of around 14.8 million shares — though the position likely reflects market-making or hedging activity rather than a directional long thesis. Broader institutional ownership remains thin, with the next 14 holders combined accounting for under 3% of shares.
With no earnings event on the calendar — USO is an ETF tracking crude oil futures — the next catalyst is entirely macro. The fund's price action, short interest trajectory, and cost to borrow are all now moving in the same direction at once: the fund up hard, shorts up hard, borrow costs up hard. The question the data leaves open is whether the cost of carrying a bearish position, now at a level that meaningfully erodes returns, eventually forces short covering — or whether the macro view on oil deteriorates fast enough to justify the expense.
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